Tire size
315/70R18 in inches
A 315/70R18 tire is 35.4 inches tall and 12.4 inches wide, on a 18-inch wheel. Written inch-style that is about 35.4x12.4R18 (an equivalent, not a size on sale). It rounds to a 35-inch tire.
| 315/70R18 | Inches | Metric |
|---|---|---|
| Overall diameter (height) | 35.4 in | 898 mm |
| Section width | 12.4 in | 315 mm |
| Sidewall height | 8.7 in | 220 mm |
| Wheel (rim) diameter | 18 in | 457 mm |
| Circumference | 111.1 in | 2822 mm |
| Revolutions | 570 per mile | 354 per km |
How it's worked out
The 70 means the sidewall is 70% of the 315 mm width: 220.5 mm, or 8.68 in. Height = wheel + 2 sidewalls = 18 + 2 x 8.68 = 35.4 in.
Similar sizes
Sizes within about 3.5% of the height of 315/70R18. The last column is your real speed at an indicated 60 mph if your speedometer was set for 315/70R18.
| Size | Height | vs 315/70R18 | Real speed at 60 mph shown |
|---|---|---|---|
| 325/60R20 | 35.4 in | -0.0% | 60.0 mph |
| 305/55R22 | 35.2 in | -0.4% | 59.7 mph |
| 315/75R17 | 35.6 in | +0.7% | 60.4 mph |
| 295/65R20 | 35.1 in | -0.7% | 59.6 mph |
| 35x12.50R15 | 35.0 in | -1.0% | 59.4 mph |
| 35x12.50R17 | 35.0 in | -1.0% | 59.4 mph |
| 35x12.50R18 | 35.0 in | -1.0% | 59.4 mph |
| 35x12.50R20 | 35.0 in | -1.0% | 59.4 mph |
Going bigger from 315/70R18
If 315/70R18 is your stock size, these are the commonly sold axle ratios that come closest to your stock overall gearing on bigger tires.
| Your ratio now | On 37s |
|---|---|
| 3.21 | 3.31 exact 3.36 |
| 3.42 | 3.55 exact 3.58 |
| 3.55 | 3.73 exact 3.71 |
| 3.73 | 3.91 exact 3.90 |
| 3.91 | 4.10 exact 4.09 |
| 4.10 | 4.30 exact 4.29 |
Exact = your ratio x new height / 35.4. Front and rear axles must match on a 4WD. Not every ratio is made for every axle. Want more pull than stock? Go one step shorter. More in the regearing guide.
Questions
How tall is a 315/70R18 tire in inches?
35.4 inches (898 mm). That is the nominal height: the 18-inch wheel plus two 8.68-inch sidewalls.
What is 315/70R18 in inches?
35.4x12.4R18: 35.4 inches tall, 12.4 inches wide, for a 18-inch wheel.
Is 315/70R18 a 35-inch tire?
It measures 35.4 inches on paper, so it rounds to 35. Real tires vary a little by brand, load and wear, so check the maker's spec sheet if a fraction of an inch matters.
How many revolutions per mile does 315/70R18 do?
About 570 per mile (354 per km), from its nominal circumference of 111.1 inches.
Nominal dimensions, calculated from the size marking. Real tires differ slightly by brand, rim width, pressure and wear. Fitment depends on your vehicle, lift and wheels: this page doesn't say whether a size fits. Updated 2026-11-14.